NZ: Home of the world's fastest spiders

An unassuming spider species which lives in New Zealand and only one other place in the world has been found to have a remarkable skill -- a lightning-fast strike to catch prey.

The mecysmaucheniidae, or trap-jaw spider, are tiny arachnids which hunt for prey on the ground, and new research has dug a bit deeper into how they feed.

Published in Current Biology today, the study by the Smithsonian Institution shows the high-speed, power-amplified strike has evolved at least four times within the family of spiders.

"This research shows how little we know about spiders and how much there is still to discover," lead author Hannah Wood says.

She made high-speed video recordings of the spiders as they snared their prey by snapping their jaws shut with incredible power and speed.

The predatory behaviour has been seen in some species of ants, but was previously unknown in arachnids.

Her study of 14 species in the trap-jaw family showed a range of speeds, and the power of four exceeded the known power output of their muscles.

It's left the researchers with questions about where that power comes from, considering the spiders' movements can't come directly from their muscles -- especially the short times and distances covered during their strike.

They believe the spiders are able to store energy to produce their quick movements.

Anatomical differences in the faster, stronger trap-jaw spiders have already been documented, but Ms Wood says they aren't quite sure how it works and more research needs to be done.

Dr Cor Vink, curator of natural history at Canterbury Museum, can't fathom why the trap-jaw would need to attack in this way.

"I can't imagine why these spiders would have evolved such an elaborate prey capture mechanism. They don't seem to have specialised in any particular prey and have been reported to feed on a range of insects and spiders."

The spiders are also found in southern South America and are one of around 2000 spider species in New Zealand -- around 95 percent are endemic, with at least 700 species undescribed.

Associate Professor in the School of Biological Sciences at the University of Canterbury believes the spider's small stature -- they're only a few millimetres long at most -- is probably why their fast strike hadn't been noticed before.

She says the find isn't surprising given how little is known about spiders.

The spider's speed perhaps allows it to attack its prey efficiently or possibly take larger prey than other spiders can manage, Dr Greg Holwell, from Auckland University's School of Biological Sciences who wasn't involved in the study, suggests.

But the trap-jaw spider doesn't have the fastest strike on record -- that honour goes to another spider species, Zearchaea, which also lives in New Zealand.